U.S. patent number 4,462,616 [Application Number 06/442,566] was granted by the patent office on 1984-07-31 for record material.
This patent grant is currently assigned to The Wiggins Teape Group Limited. Invention is credited to Kenneth J. Shanton.
United States Patent |
4,462,616 |
Shanton |
July 31, 1984 |
Record material
Abstract
Pressure- or heat-sensitive record material carries hydrated
zirconia as a color developer material. The hydrated zirconia may
be modified by the presence of compounds or ions of one or more
multivalent metals.
Inventors: |
Shanton; Kenneth J.
(Beaconsfield, GB2) |
Assignee: |
The Wiggins Teape Group Limited
(Hampshire, GB2)
|
Family
ID: |
10526372 |
Appl.
No.: |
06/442,566 |
Filed: |
November 18, 1982 |
Foreign Application Priority Data
Current U.S.
Class: |
503/210; 428/330;
428/913; 428/914; 503/211; 503/212; 503/219; 503/225 |
Current CPC
Class: |
B41M
5/1555 (20130101); Y10T 428/258 (20150115); Y10S
428/914 (20130101); Y10S 428/913 (20130101) |
Current International
Class: |
B41M
5/155 (20060101); B41M 005/16 (); B41M 005/18 ();
B41M 005/22 () |
Field of
Search: |
;282/27.5 ;427/150-153
;428/330,320.4-320.8,411,488,537,913,914 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2364255 |
|
Jul 1975 |
|
DE |
|
3034486 |
|
Nov 1979 |
|
DE |
|
666437 |
|
Jun 1949 |
|
GB |
|
1271304 |
|
Apr 1972 |
|
GB |
|
1451982 |
|
Oct 1976 |
|
GB |
|
1467003 |
|
Mar 1977 |
|
GB |
|
1497663 |
|
Jan 1978 |
|
GB |
|
Primary Examiner: Hess; Bruce H.
Attorney, Agent or Firm: Burns, Doane, Swecker &
Mathis
Claims
I claim:
1. Record material carrying hydrated zirconia as a colour
developer.
2. Record material as claimed in claim 1, characterized in that the
hydrated zirconia is modified by the presence of a compound or ions
of a multivalent metal.
Description
This invention relates to record material and to a process for the
production of the record material. The record material may be, for
example, part of a pressure-sensitive copying system or of a
heat-sensitive recording system.
In one known type of pressure-sensitive copying system, usually
known as a transfer system, an upper sheet is coated on its lower
surface with microcapsules containing a solution of one or more
colourless colour formers and a lower sheet is coated on its upper
surface with a colour developing co-reactant material. A number of
intermediate sheets may also be provided, each of which is coated
on its lower surface with microcapsules and on its upper surface
with colour developing material. Pressure exerted on the sheets by
writing or typing ruptures the microcapsules, thereby releasing the
colour former solution on to the colour developing material on the
next lower sheet and giving rise to a chemical reaction which
develops the colour of the colour former. In a variant of this
system, the microcapsules are replaced by a coating in which the
colour former solution is present as globules in a continuous
matrix of solid material.
In another type of pressure-sensitive copying system, usually known
as a self-contained or autogeneous system, microcapsules and colour
developing co-reactant material are coated onto the same surface of
a sheet, and writing or typing on a sheet placed above the
thus-coated sheet causes the microcapsules to rupture and release
the colour former, which then reacts with the colour developing
material on the sheet to produce a colour.
Heat-sensitive recording systems frequently utilise the same type
of reactants as those described above to produce a coloured mark,
but rely on heat to convert one or both reactants from a solid
state in which no reaction occurs to a liquid state which
facilitates the colour-forming reaction, for example by dissolution
in a binder which is melted by the heat applied.
The sheet material used in such systems is usually of paper,
although in principle there is no limitation on the type of sheet
which may be used. When paper is used, the colour developing
co-reactant material and/or the microcapsules may be present as a
loading within the sheet material instead of as a coating on the
sheet material. Such a loading is conveniently introduced into the
papermaking stock from which the sheet material is made.
Zirconia, i.e. zirconium dioxide, ZrO.sub.2, has long been
recognised as a material suitable as a co-reactant for developing
the colour of colour formers for use in record material, see for
example U.S. Pat. Nos. 2,505,470 and 2,777,780. However, whilst it
is quite effective when in powder form for developing the colour of
a solution of a colour former such as crystal violet lactone, it is
much less effective when coated on to paper as the active component
of a colour developer composition, probably because its reactivity
is suppressed by the presence of conventional paper coating
binders, for example latex binders. A further problem is that the
colour developed initially is very prone to fading.
It has now unexpectedly been found that hydrated zirconia affords
good colour developing properties whilst being much less
susceptible to the problems which are experienced with zirconia,
particularly if the hydrated zirconia is modified by the presence
of suitable metal compounds or ions. Hydrated zirconia, which is
alternatively known as hydrous zirconia, may be represented by the
formula ZrO.sub.2.xH.sub.2 O.
According to a first aspect of the invention, there is provided
record material carrying hydrated zirconia as a colour
developer.
According to a second aspect of the invention, there is provided a
process for the production of record material, comprising the steps
of:
(a) forming an aqueous dispersion of hydrated zirconia;
(b) either:
(i) formulating said dispersion into a coating composition and
applying the coating composition to a substrate web; or
(ii) introducing said dispersion into papermaking stock and forming
a paper web which incorporates said composite as a loading; and
(c) drying the resulting coated or loaded web to produce said
record material.
The hydrated zirconia used in the present process may have been
prepared previously, for example it may be a commercially available
material or it may be precipitated in an aqueous medium, as an
initial stage in the process for preparing the record material. The
hydrated zirconia may be precipitated from the aqueous medium in
various ways, for example by precipitation from an aqueous solution
of a zirconium salt on addition of aqueous alkali; by addition of
an aqueous solution of a zirconium salt to excess aqueous alkali,
followed by neutralization; or by mixing an aqueous solution of a
zirconium salt and an aqueous alkali in proportions such as to
maintain a substantially neutral pH throughout the mixing stage.
The zirconium salt may for example be zirconyl chloride or
zirconium sulphate. The aqueous alkali may for example be a
solution of sodium, potassium, lithium or ammonium hydroxide.
Instead of the use of a cationic zirconium salt, the hydrated
zirconia may be precipitated from a solution of a zirconate, for
example ammonium tris-carbonato zirconate, by addition of acid, for
example a mineral acid such as sulphuric acid or hydrochloric
acid.
In a preferred embodiment of the present invention, the hydrated
zirconia is modified by the presence of a compound or ions of one
or more multivalent metals, for example copper, nickel, manganese,
cobalt, chromium, zinc, magnesium, titanium, tin, calcium,
tungsten, iron, tantalum, molybdenum or niobium. Such modification
will hereafter be referred to as "metal modification".
Metal modification may conveniently be brought about by treating
the hydrated zirconia, once formed, with a solution of the metal
salt, for example of the sulphate or chloride. Alternatively, a
solution of the metal salt may be introduced into the medium from
which the hydrated zirconia is precipitated.
The precise nature of the species formed during metal modification
has not so far been fully elucidated, but one possibility is that a
metal oxide or hydroxide is precipitated so as to be present in the
hydrated zirconia. An alternative or additional possibility is that
ion-exchange occurs so that metal ions are present at ion-exchange
sites on the surface of the hydrated zirconia.
Metal modification enables improvements to be obtained in the
initial intensity and/or fade resistance of the print obtained from
hydrated zirconia with both so-called rapid-developing and
so-called slow developing colour formers, and with colour formers
intermediate to these categories.
Categorisation of colour formers according to the speed with which
their colour may be developed has long been a common practice in
the art. 3,3-Bis (4'-dimethylaminophenyl)-6-dimethylaminophthalide
(CVL) and similar lactone colour formers are typical of the
rapid-developing class, in which colour formation results from
cleavage of the lactone ring on contact with an acid co-reactant.
10-Benzoyl-3,7-bis(dimethylamino)phenothiazine (more commonly known
as benzoyl leuco methylene blue or BLMB) and
10-benzoyl-3,7-bis(diethylamino) phenoxazine (also known as BLASB)
are examples of the slow-developing class. It is generally believed
that formation of a coloured species is a result of slow hydrolysis
of the benzoyl group over a period of up to about two days,
followed by aerial oxidation. Spiro-bipyran colour formers, which
are widely disclosed in the patent literature, are examples of
colour formers in the intermediate category.
The effect achieved by metal modification depends in substantial
measure on the particular metal involved and on the particular
colour former(s) being used, as will become clear from
consideration of the Examples set out hereafter.
The production of hydrated zirconia by any of the process routes
described earlier may take place in the presence of a polymeric
rheology modifier such as the sodium salt of carboxymethylcellulose
(CMC), polyethyleneimine or sodium hexametaphosphate. The presence
of such a material modifies the rheological properties of the
resulting dispersion of hydrated zirconia and thus results in a
more easily agitatable, pumpable and coatable composition, possibly
by having a dispersing or flocculating action. It may be
advantageous to precipitate the hydrated zirconia in the presence
of a particulate material which may function as a carrier or
nucleating agent. Suitable particulate materials for this purpose
include kaolin, calcium carbonate or other materials commonly used
as pigments, fillers or extenders in the paper coating art, since
these materials will often need to be included in the coating
composition used in the production of a coated record material or
in the papermaking stock used in the production of a loaded record
material.
A coating composition for use in the production of the present
record material will normally also contain a binder (which may be
wholly or in part constituted by the CMC optionally used as a
rheology modifier during the preparation of the colour developing
material) and/or a filler or extender, which typically is kaolin,
calcium carbonate or a synthetic paper coating pigment, for example
a urea-formaldehyde resin pigment. The filler or extender may be
wholly or in part constituted by the particulate material which may
be used during the preparation of the hydrated zirconia. In the
case of a loaded record material, a filler or extender may also be
present, and again this may be wholly or in part constituted by the
particulate material which may be used during the preparation of
the hydrated zirconia.
The pH of the coating composition influences the subsequent colour
developing performance of the composition, and also its viscosity,
which is significant in terms of the ease with which the
composition may be coated on to paper or other sheet material. The
preferred pH for the coating composition is within the range 5 to
9.5, and is preferably around 7.0. Sodium hydroxide is conveniently
used for pH adjustment, but other alkaline materials may be used,
for example potassium hydroxide, lithium hydroxide, calcium
hydroxide or ammonium hydroxide.
The aqueous dispersion which is formulated into the coating
composition or introduced into the papermaking stock may be a
dispersion obtained as a result of precipitation of hydrated
zirconia from an aqueous medium. Alternatively, the hydrated
zirconia may be separated after its preparation, e.g. by filtering
off, and then washed to remove soluble salts before being
re-dispersed in a further aqueous medium to form the dispersion for
formulation into the coating composition or introduction into the
papermaking stock. The latter procedure tends to give rise to more
intense colour developing properties.
The hydrated zirconia may be used as the only colour developing
material in a colour developing composition, or it may be used in
simple admixture with other conventional colour developing
materials, e.g. an acid-washed dioctahedral montmorillonite clay.
It will be appreciated however that such admixtures are to be
distinguished from colour developing composites or reaction
products of hydrated zirconia with inorganic materials such as
hydrated silica and/or hydrated alumina, or organic materials such
as aromatic carboxylic acids, which are not within the scope of the
present invention.
It is usually desirable to treat the hydrated zirconia in order to
break up any aggregates which have formed, for example by
ball-milling. This treatment may be carried out either before or
after the optional addition of fillers and/or additional colour
developing materials.
In the case of a coated record material, the record material may
form part of a transfer or self-contained pressure-sensitive
copying system or of a heat-sensitive recording system as described
previously. In the case of a loaded record material, the record
material may be used in the same manner as the coated record
material just described, or the record material may also carry
microencapsulated colour former solution as a loading, so as to be
a self-contained record material.
The invention will now be illustrated by the following Examples (in
which all percentages quoted are by weight):
Example 1
This illustrates the preparation of hydrated zirconia by
precipitation from an initially acidic medium.
1.2 g of CMC (FF5 supplied by Finnfix) were dissolved in 105 g of
de-ionized water over a period of 15 minutes with stirring. 45 g of
zirconyl chloride, ZrOCl.sub.2.8H.sub.2 O were then added, giving
an acidic solution, and sufficient 40% w/w sodium hydroxide
solution was added slowly with stirring to return the pH to 7, with
resultant precipitation of hydrated zirconia.
The mixture was left stirring for an hour. 10 g of kaolin (Dinkie A
supplied by English China Clays) were then added and the mixture
was stirred for 30 minutes after which 10.0 g of styrene-butadiene
latex (Dow 675) were added. The pH was re-adjusted to 7. The
resulting mixture was then left stirring overnight before being
coated on to paper at a nominal dry coatweight of 8 gm.sup.-2 using
a laboratory Meyer bar coater. The coated sheet was dried and
calendered and then subjected to calender intensity and fade
resistance tests to assess its performance as a colour developing
material.
The calender intensity test involved superimposing a strip of paper
coated with encapsulated colour former solution on a strip of the
coated paper under test, passing the superimposed strips through a
laboratory calender to rupture the capsules and thereby produce a
colour on the test strip, measuring the reflectance of the coloured
strip (I) and expressing the results (I/Io) as a percentage of the
reflectance of an unused control strip (Io). Thus the lower the
calender intensity value (I/Io) the more intense the developed
colour. The calender intensity tests were done with two different
papers, designated hereafter as Papers A and B. Paper A employed a
commercially used blue colour former blend containing, inter alia,
CVL as a rapid-developing colour former and BLASB as a
slow-developing colour former. Paper B employed a commercially used
black colour former blend also including CVL and BLASB.
The reflectance measurements were done both two minutes after
calendering and again after forty-eight hours, the samples being
kept in the dark in the interim. The colour developed after two
minutes is primarily due to the rapid-developing colour formers,
whereas the colour after forty-eight hours derives also from the
slow-developing colour formers, (fading of the colour from the
rapid-developing colour formers also influences the intensity
achieved).
The fading test involved positioning the developed strips (after
forty-eight hours development) in a cabinet in which were an array
of daylight fluorescent striplamps. This is thought to simulate, in
accelerated form, the fading which a print might undergo under
normal conditions of use. After exposure for the desired time,
measurements were made as described with reference to the calender
intensity test, and the results were expressed in the same way.
The calender intensity and fade resistance results were as
follows:
______________________________________ Test Conditions Paper A
Paper B ______________________________________ 2 min. development
59.9 65.6 48 hours development 43.4 49.8 1 hour fade 42.3 47.3 3
hours fade 45.3 49.1 5 hours fade 48.5 51.7 10 hours fade 55.2 57.6
15 hours fade 62.5 63.5 ______________________________________
Example 2
This illustrates the precipitation of hydrated zirconia from an
initially alkaline medium.
1.2 g of CMC (FF5) were dissolved in 105 g of deionized water over
a period of 15 minutes with stirring, and sufficient sodium
hydroxide solution was added to give a pH of 10.0. 45 g of zirconyl
chloride, ZrOCl.sub.2.8H.sub.2 O were then added slowly with
stirring, and the pH was then adjusted to 7 by the slow addition of
40% w/w sulphuric acid. The mixture was left stirring for an hour.
10 g of kaolin (Dinkie A) were then added and the mixture was
stirred for 30 minutes, after which 10.0 g of styrene-butadiene
latex (Dow 675) were added. The resulting mixture was then left
stirring overnight before being coated on to paper with a nominal
dry coatweight of 8 gm.sup.-2 using a laboratory Meyer bar coater.
The coated sheet was dried and calendered and then subjected to
calender intensity and fade resistance tests to assess its
performance as a colour developing material.
The calender intensity and fade resistance results were as
follows:
______________________________________ Test Conditions Paper A
Paper B ______________________________________ 2 min. development
61.4 65.8 48 hour development 48.7 52.9 1 hour fade 45.0 47.0 3
hour fade 51.4 50.3 5 hour fade 54.5 54.3 10 hour fade 63.0 61.3 15
hour fade 69.3 63.5 ______________________________________
Example 3
This illustrates the precipitation of hydrated zirconia from a
neutral medium.
1.2 g of CMC (FF5) were dissolved in 30 g of de-ionized water over
a period of 15 minutes with stirring. A solution of 45 g zirconyl
chloride, ZrOCl.sub.2.8H.sub.2 O in 75 g de-ionized water was then
added dropwise, and simultaneously sodium hydroxide solution was
added in an amount sufficient to maintain a substantially constant
pH of 7. The mixture was left stirring for an hour. 10 g of kaolin
(Dinkie A) were then added and the mixture was stirred for 30
minutes, after which 10.0 g of styrene-butadiene latex (Dow 675)
were added. The resulting mixture was then left stirring overnight
before being coated on to paper at a nominal dry coatweight of 8
gm.sup.-2 using a laboratory Meyer bar coater. The coated sheet was
dried and calendered and then subjected to calender intensity and
fade resistance tests to assess its performance as a colour
developing material.
The calender intensity and fade resistance results were as
follows:
______________________________________ Test Conditions Paper A
Paper B ______________________________________ 2 min. development
64.3 68.2 48 hour development 51.1 56.5 1 hour fade 49.1 51.9 3
hour fade 52.7 54.5 5 hour fade 56.9 57.2 10 hour fade 62.1 61.4 15
hour fade 66.6 66.2 ______________________________________
Example 4
This illustrates the performance of hydrated zirconia as a colour
developer for various colour formers, using a coating composition
prepared in the same manner as described in Example 1.
The calender intensity and fade resistance results with a series of
papers (Papers C to G) carrying capsules containing a single colour
former in solution were as follows:
______________________________________ Test Condition C D E F G H*
______________________________________ 2 min development 76.9 100
70.6 68.5 99.6 81.7 48 hour development 75.9 82.0 62.7 64.1 78.7
77.6 1 hour fade 76.2 75.7 62.5 63.2 65.9 77.5 3 hour fade 78.7
73.0 68.6 64.8 66.2 77.6 5 hour fade 80.7 72.6 73.7 67.0 66.4 77.9
10 hour fade 87.8 71.9 83.1 72.3 68.7 80.5 15 hour fade 92.1 71.3
92.1 75.5 74.2 81.4 ______________________________________
The encapsulated colour former(s) carried by Papers C to G were as
follows:
Paper C--"Pergascript Olive I-G", a green-black colour former sold
by Ciba-Geigy
Paper D--BLASB
Paper E--CVL
Paper F--"Pyridyl Blue", i.e. one or both of the isomeric compounds
5-(1'-ethyl-2'-methylindol-3'-yl)-5-4"-diethylamino-2"-ethoxyphenyl)-5,7-d
ihydrofuro(3,4-b)pyridin-7-one and
7-(1'-ethyl-2'-methylindol-3'-yl)-7-(4"-diethylamino-2"-ethoxyphenyl)-5,7-
dihydrofuro(3,4-b)pyridin-5-one
Paper G--"Pergascript Blue BP 558"--a slow-developing blue colour
former sold by Ciba-Geigy
Paper H--"Indolyl Red", i.e.
3,3-bis(1'-ethyl-2'-methylindol-3'-yl)phthalide.
In all cases except for colour former H the colour former was
present as a 1% solution in a solvent blend comprising partially
hydrogenated terphenyls (80%) and kerosene (20%). Colour former H
was applied as a 0.65% solution in a solvent blend comprising
partially hydrated terphenyls (75%) and kerosene (25%).
Example 5
This repeated the procedure of Example 1, but the coating
composition obtained after the addition of kaolin and latex was
coated on to paper shortly after it had been prepared, rather than
being stored overnight. This resulted in improved colour developing
performance, as can be seen from the calender intensity and fade
resistance results obtained with Papers A and B, which were as
follows:
______________________________________ Test Conditions Paper A
Paper B ______________________________________ 2 mins. development
54.3 60.0 48 hour development 37.3 44.3 1 hour fade 37.2 43.2 3
hour fade 42.0 45.0 5 hour fade 46.4 48.7 10 hour fade 55.2 54.6 15
hour fade 57.5 59.2 ______________________________________
Example 6
This illustrates the use of zirconium sulphate rather than zirconyl
chloride as the source of zirconium.
The procedure used was as described in Example 1 except that the
following quantities of material were used:
______________________________________ de-ionized water 57.5 g CMC
0.6 g zirconium sulphate, Zr(SO.sub.4).sub.2.4H.sub.2 O 25.0 g
kaolin 5.0 g latex 5.0 g ______________________________________
The calender intensity results obtained with Papers A, B and E were
as follows:
______________________________________ Test Paper Paper Paper
Conditions A B E ______________________________________ 2 min.
development 66.4 70.8 73.0 48 hour development 48.8 56.6 67.1
______________________________________
Example 7
This illustrates the use of alternative alkaline materials
(lithium, potassium and ammonium hydroxides) to the sodium
hydroxide solution used in the previous Examples. The procedure was
as described in Example 1, and the calender intensity results
obtained with Papers A, B and E were as follows:
______________________________________ Alkali Test LiOH KOH
NH.sub.4 OH Condi- Paper Paper Paper tions A B E A B E A B E
______________________________________ 2 min. 62.2 66.6 70.4 69.4
74.0 73.4 74.1 73.0 84.4 development 48 hour 45.3 51.9 65.7 42.6
52.8 59.2 55.1 56.5 76.0 development
______________________________________
Example 8
This illustrates the effect of ball-milling the coating
composition. The procedure was as described in Example 6 (using
zirconium sulphate) except that after the addition of kaolin and
latex, the mixture was ball-milled overnight to give a mean
particle size of approximately 3.mu. when measured by the Andreasen
Sedimentation Pipette method. The results of calender intensity and
fade resistance tests with Papers A, B and E were as follows:
______________________________________ Test Conditions Paper A
Paper B Paper E ______________________________________ 2 min.
development 63.7 68.5 71.5 48 hour development 44.7 52.8 62.4 1
hour fade 44.0 48.6 66.4 15 hour fade 63.5 60.1 89.6
______________________________________
It will be seen that ball-milling gave slightly improved colour
developing performance.
Example 9
This illustrates the production of copper-modified hydrated
zirconia.
The procedure employed was as in Example 1, except that after
hydrated zirconia was precipitated by adjusting the pH to 7, 20 g
of 25% w/w solution of copper sulphate, CuSO.sub.4.5H.sub.2 O were
slowly added, and the pH was re-adjusted to 7 if necessary.
Stirring was then contained for a further hour before continuing
the Example 1 procedure by the addition of kaolin.
A parallel preparation omitting the addition of copper sulphate
solution was also carried out for comparison purposes.
The sheets prepared were subjected to calender intensity and fade
resistance tests with Papers A and B, and the results were as
follows:
______________________________________ Test Copper modified
Unmodified Conditions Paper A Paper B Paper A Paper B
______________________________________ 2 min. development 43.5 56.7
52.3 60.5 48 hour development 40.9 46.9 42.0 52.6 16 hour fade 45.7
50.7 66.9 68.5 ______________________________________
It will be seen that copper modification resulted in a significant
improvement in initial intensity and a major improvement in fade
resistance.
Example 10
This illustrates the use of a range of different metals in the
production of metal-modified hydrated zirconia.
The procedure described in Example 9 was repeated, except that in
place of the copper sulphate solution, the following were used:
______________________________________ Material Wt (g)
______________________________________ (a) calcium sulphate
CaSO.sub.4 2.2 (b) cobalt sulphate CoSO.sub.4.7H.sub.2 O 4.5 (c)
magnesium sulphate MgSO.sub.4 1.9 (d) nickel sulphate
NiSO.sub.4.7H.sub.2 O 4.2 (e) zinc sulphate ZnSO.sub.4.7H.sub.2 O
4.6 (f) tin chloride SnCl.sub.4.5H.sub.2 O 5.6
______________________________________
A repeat of the procedure with copper sulphate was also carried
out, together with a procedure in which no modifying metal was
used.
The resulting papers were tested for calender intensity and fade
resistance and the results were as follows:
______________________________________ Modifying metal Test Ca Co
Conditions Paper A Paper B Paper A Paper B
______________________________________ 2 min. development 46.1 53.6
62.0 63.6 48 hour development 37.2 43.9 48.0 48.7 1 hour fade 37.6
42.2 63.6 57.9 3 hour fade 44.5 47.6 65.3 58.8 5 hour fade 49.9
52.9 65.2 60.2 10 hour fade 61.1 61.3 68.5 62.1 15 hour fade 67.0
66.7 70.3 64.7 30 hour fade 73.1 77.5 71.9 66.5 50 hour fade 79.1
83.1 77.1 71.7 100 hour fade 91.3 92.6 82.8 79.0
______________________________________
______________________________________ Modifying metal Test Mg Ni
Conditions Paper A Paper B Paper A Paper B
______________________________________ 2 min. development 48.5 56.6
47.0 55.6 48 hour development 39.9 47.0 38.1 46.3 1 hour fade 38.8
44.1 37.2 42.3 3 hour fade 45.3 48.2 38.0 44.6 5 hour fade 51.4
53.7 40.8 46.1 10 hour fade 63.6 62.3 47.3 49.5 15 hour fade 67.7
67.5 52.6 54.6 30 hour fade 75.7 77.7 56.2 59.0 50 hour fade 82.8
85.0 64.3 65.6 100 hour fade 91.4 93.4 72.9 77.0
______________________________________
______________________________________ Modifying metal Test Zn Sn
Conditions Paper A Paper B Paper A Paper B
______________________________________ 2 min. development 43.8 51.9
46.9 54.7 48 hour development 35.3 43.6 38.6 46.6 1 hour fade 36.0
42.1 41.9 45.1 3 hour fade 42.9 46.2 50.4 57.6 5 hour fade 47.8
50.5 57.4 58.7 10 hour fade 58.4 58.4 66.2 66.6 15 hour fade 64.0
63.7 70.3 72.2 30 hour fade 72.3 71.5 78.7 81.1 50 hour fade 80.1
78.9 84.6 86.3 100 hour fade 90.8 90.5 93.1 94.5
______________________________________
______________________________________ Modifying metal Test Cu None
Conditions Paper A Paper B Paper A Paper B
______________________________________ 2 min. development 53.9 54.3
63.0 67.5 48 hour development 39.9 45.7 46.0 51.5 1 hour fade 39.8
46.0 44.3 48.1 3 hour fade 40.2 46.8 50.9 51.6 5 hour fade 44.8
48.5 58.0 57.4 10 hour fade 50.0 52.5 66.7 63.9 15 hour fade 56.4
56.2 74.8 70.1 30 hour fade 62.6 62.7 80.9 78.5 50 hour fade 72.9
67.9 87.3 85.9 100 hour fade 78.3 77.0 95.7 --
______________________________________
It will be seen that all the modifying metals improved initial
intensity and fade resistance compared with unmodified hydrated
zirconia, with both Papers A and B, except for zinc modified
zirconia with Paper B. Zinc modification did however markedly
improve initial intensity, and gave significantly improved fade
resistance with Paper A.
Comparative Example 1
This compares the colour developing properties of hydrated zirconia
with that of a commercially available zirconium dioxide (that
supplied as a laboratory reagent by BDH Chemicals).
45 g of zirconyl chloride were dissolved in 150 g of de-ionized
water, and the pH was adjusted to 7 by the addition of aqueous
ammonia with stirring. A white precipitate was obtained. The
precipitate was separated by filtration and then washed with
de-ionized water, after which it was dried for three hours at
30.degree. C. in a laboratory fluid bed drier. The dried material
was then ground using a mortar and pestle to give a fine white
powder approximating in fineness to that of the BDH zirconium
dioxide.
1 g samples of the ground dried hydrated zirconia and of the BDH
zirconium dioxide were each stirred overnight with 10 g of a 0.1%
w/w solution of CVL in toluene. Each mixture was blue. The toluene
was removed in each case by filtration, and the filtered off blue
powders were each washed with toluene to remove any excess CVL,
after which they were air-dried. To the naked eye, the hydrated
zirconia sample was of a noticeably more intense blue colour than
the zirconium dioxide.
Each sample was then placed in the sample holder of a MacBeth
MS-2000 spectrophotometer, and its reflectance spectrum was
obtained. In order to permit proper comparison of the colour
developing performance of the two samples, Kubelka-Munk functions
(K/S) at 20 nm wavelength intervals were derived from the
reflectance data by computer processing. The greater the K/S value,
the more intense the colour. At the wavelength of maximum
absorption (600 nm), the K/S value for hydrated zirconia was 2.43,
and that for BDH zirconium dioxide was 1.29, indicating that the
colour developing performance of the hydrated zirconia was much
superior to that of the BDH zirconium dioxide.
Comparative Example 2
This compares the performance of a colour developer sheet in
accordance with the present invention with a colour developer sheet
carrying a commercially available non-hydrated zirconia (Fisons SLR
grade) as a colour developer.
The colour developer sheet according to the invention was prepared
as follows:
130.9 g of 30% w/w solution of zirconyl chloride,
ZrOCl.sub.2.8H.sub.2 O were dissolved in 305.4 g of de-ionized
water and 113.8 g of 10N sodium hydroxide solution were added
rapidly with stirring to give a pH of 7.0. A white precipitate of
hydrated zirconia was obtained. This precipitate was filtered off,
washed and redispersed in de-ionized water, and the procedure
repeated until the dispersion was free of chloride ions, as
determined by the silver nitrate test. This dispersion was then
passed through a continuous laboratory ball mill, after which it
was filtered. The precipitate was then re-dispersed in de-ionized
water and 17.6 g of 50% solids content styrene-butadiene latex
binder (Dow 675) were added, so as to give a 15% latex content on a
dry weight basis. The pH was adjusted to 7.0 and sufficient
de-ionized water was added to lower the viscosity of the mixture to
a level suitable for coating using a laboratory Meyer Bar coater.
The mixture was then coated on to paper at a nominal dry coatweight
of 8 gm.sup.-2, and the coated sheet was dried and calendered.
The colour developer sheet carrying non-hydrated zirconia was made
by slurrying 50 g of zirconia in 75 g of de-ionized water, and then
repeating the procedure described above from the stage of adding
latex onwards.
The sheets were each subjected to calendar intensity tests, and the
results were as follows:
______________________________________ Test Colour Developer
Conditions Hydrated Zirconia Zirconia
______________________________________ 2 min. development 44.4 88.4
48 hour development 34.5 79.0
______________________________________
It will be seen that although zirconia functions as a colour
developer, the sheet carrying hydrated zirconia showed markedly
superior colour developer properties.
Example 11
This demonstrates the suitability of a typical example of a colour
developer according to the invention for use in heat-sensitive
record material.
20 g of a washed and dried hydrated zirconia prepared by the method
of Comparative Example 2 were mixed with 48 g of stearamide wax and
ground in a pestle and mortar. 45 g of de-ionized water and 60 g of
10% w/w poly(vinyl alcohol) solution (that supplied as "Gohsenol
GLO5" by Nippon Gohsei of Japan) were added and the mixture was
ball-milled overnight. A further 95 g of 10% w/w poly(vinyl
alcohol) solution were then added, together with 32 g de-ionized
water.
In a separate procedure, 22 g of a black colour former
(2'-anilino-6'-diethylamino-3'-methylfluoran), were mixed with 42 g
de-ionized water and 100 g of 10% w/w poly(vinyl alcohol) solution,
and the mixture was ball-milled overnight.
The suspensions resulting from the above procedures were then mixed
and coated on to paper by means of a laboratory Meyer bar coater at
a nominal coat weight of 8 gm.sup.-2. The paper was then dried.
On subjecting the coated surface to heat, a black colouration was
obtained.
* * * * *